SINUOUS ORDINARY EPIDERMAL-CELLS - BEHIND SEVERAL PATTERNS OF WAVINESS, A COMMON MORPHOGENETIC MECHANISM

Morphogenesis of sinuous epidermal cells in leaves of the fern Aspleni um nidus and the monocotyledonous Cyperus papyrus, petals of the dicot yledonous Begonia lucerna, and in-vitro-grown leaves of the fern Adian tum capillus-veneris is controlled by the local differentiation of the ir walls. In all these cases wall pads, including radial cellulose mic rofibrils, are deposited at the junctions of the external periclinal w all with the anticlinal ones. Moreover, in Asplenium nidus, similar wa ll pads form at the junctions of the internal periclinal wall with the anticlinal ones. The wall pads are connected to anticlinal cellulose microfibril bundles running the whole depth of the anticlinal walls or part of it. This wall differentiation imposes a highly controlled cel l wall expansion, a consequence of which is the waviness of the epider mal cell anticlinal walls. The pattern of a all reinforcement varies a mong different species, resulting in differences in the pattern of wav iness. Cortical microtubule arrays mirror the orientated deposition of cellulose microfibrils in the epidermal cells. These findings, derive d from plants from different major groups, show a common epidermal cel l morphogenetic mechanism depending on radial cellulose microfibrils a nd cellulose microfibril bundles. The facts that (a) epidermal cell mo rphogenesis in Adiantum capillus-veneris leaves grown in vitro differs considerably from that of typical leaves and (b) petal epidermal cell s in Begonia lucerna are sinuous, while leaf epidermal cells are not, suggest that this mechanism may be affected by epigenetic factors.